Some water meters and gas meters are equipped with a wireless device for transmitting meter readings by wireless. A meter disclosed in Patent Literature 1 includes a wireless device inside a meter casing. A meter reading measured by the meter is sent outside by the wireless device. Accordingly, meter readings can be collected at a place far from the meter by using wireless transmission. In addition, meter readings from multiple meters can be collected at one place.
However, this conventional meter includes the wireless device inside the meter casing. The meter is often installed in a highly-humid environment. This often causes dew condensation by difference between temperature of water or gas passing through the meter and ambient temperature. In other words, the wireless device in the conventional meter has disadvantages such as erroneous operation of electronic circuit, degradation of wireless performance, and degradation of insulation performance due to influence of moisture such as dew condensation water.    [PTL 1] Japanese Patent Unexamined Publication No. H11-86174